Question : router causing problems existing lan

we have a lan setup, everything is working fine..  setup is below:
Comcast SMC (modem/gateway) -> Juniper Netscreen -> Linksys 24p Switch -> SBS2003 Server and Workstations

we've recently come across the need for wireless access.  had a spare wireless n router sitting around..  linksys WRT120N.  googled is and it says "home router" but i couldn't find any specs on what made it a "home router"..  anyway..  one of the ports from linksys switch goes to our warehouse computer.  the need for wireless is in the warehouse, so it seemed to make sense to put the router there.  used cat5 from warehouse computer, hooked up router, then connected warehouse computer to router.  as of this morning, the router and the warehouse computer were both receiving unique ips from SBS2003 server, and able to connect to network, shares, internet, etc.  all is well.  or so i thought..

then i start getting calls from people around the building..  (NOT connected to the wireless router..  these are people connected right to Linksys).  they are able to browse internet and network resources fine.  but when they try to send/receive in outlook 2003, it hangs when connecting to outbound and inbound mail servers.  the really odd part is that every 4 or 5 times..  it will send/receive successfully.  no common denominator i can find, users are all in same ou, and problem is happening across 2 different domains hosted on 2 different servers..  so i don't think it's anything on the hosting end.  have disabled DHCP on the new router, and also disabled the firewall settings.  it should be acting basically as an access point.  
when i remove the router from the setup, everything send/receives correctly.  these are pop3 mailboxes hosted by a company, not an exchange server.  i am only getting the errors from certain pcs.  for instance, i have emails on both domains that are having this problem on my pc, but i'm able to send/receive with no problem.  

Answer : router causing problems existing lan

The term "Home Based" simply means it assumes you don't have domain servers that provide DNS and DHCP to your LAN computers. Since you do have domain servers with DHCP and DNS, you need to prevent your "Home Based" router from providing these services.

Your wireless router may be trying to supply DHCP to your clients that have wireless cards on thier computers. In doing so, by default, it will also try to supply DNS. This is how most home based routers are configured.

It's not the DHCP part that knocks them down unless your server sees it as a rogue DHCP server. The problem is the DNS part when dealing with email. The preferred DNS servers on your "HOME BASED" router will be outside servers. So, they skip the domain servers for DNS if your wireless router is supplying DHCP.

Prevent your home based wireless router from providing DHCP to any of its clients, give it a fixed IP and make sure Its preferred DNS servers and default gateway are your servers and gateway.

Most laptops come with a wireless cards and will see that router and try to get an IP from it. So, all DNS, Gateway, and DHCP will come from that and may override your Wired LAN.